Corrosion-protected anchoring rods for anchoring structural parts in the earth, as well as method of producing anchorings with corrosion-protected anchor rods

ABSTRACT

A corrosion-protected anchoring rod for the anchoring of structural parts in the earth is adapted to be placed in a bore hole formed in the earth, with the rod consisting of a force transmission section adjacent the opening of the bore hole, and a force introduction section adjacent the end of the anchoring rod disposed furthest in the hole. The force transmission section of the rod is covered with a smooth, corrosion-preventing covering, while the force introduction section is also covered with a corrosion-preventing covering having a corrogated profile in order to increase the frictional resistance between the anchoring rod and the surrounding soil. The corrosion-prevented coverings of the anchoring rod are suitably joined to completely enclose the anchoring rod, and a bonding composition is provided in the space between the corrogated covering and the tension member.

United States Patent [191 Bauer Aug. 21, 1973 [76] Inventor: Karlheinz Bauer, 8898 Willelsbacherstr. 5, Schrobenhausen/Obb., Germany 22 Filed: Mar. 31, 1971 21 Appl.No.: 129,715

{30] Foreign Application Priority Data 3,496,729 2/1970 Pleuger 61/53.6 3,494,134 2/1970 Jorge 61/35 FOREIGN PATENTS OR APPLICATIONS 848,900 0/1960 Great Britain 61/39 Primary Examiner-Jacob Shapiro Attorney-Thomas M. Marshall [5 7 ABSTRACT A corrosion-protected anchoring rod for the anchoring of structural parts in the earth is adapted to be placed in a bore hole formed in the earth, with the rod consisting of a force transmission section adjacent the opening of the bore hole, and a force introduction section adjacent the end of the anchoring rod disposed furthest in the hole. The force transmission section of the rod is covered with a smooth, corrosion-preventing covering, while the force introduction section is also covered with a corrosion-preventing covering having a corro gated profile in order to increase the frictional resistance between'the anchoring rod and'the surrounding soil. The corrosion-prevented coverings of the anchor ing rod are suitably joined to completely enclose the anchoring rod, and a bonding composition is provided in the space between the corrogated covering and the tension member.

4 Claims, 4 Drawing Figures CORROSION-PROTECTED ANCHORING RODS FOR ANCHORING STRUCTURAL PARTS IN THE EARTH, AS WELL AS METHOD OF PRODUCING ANCHORINGS WITH CORROSION-PROTECTED ANCHOR RODS The present invention relates to a corrosionprotected anchor rod for the anchoring of structural parts in a bore hole in the earth, the anchor rod consisting of a steel tension member the force transmission section of which, i.e., the section closest to the opening in the earth, is provided with a smooth, corrosionpreventing covering, and the force introduction section of which, i.e., the section of the anchor rod disposed furthest in the bore hole, comprises a small sized body having a high coefficient of friction.

The invention furthermore concerns a method of producing anchorings in the earth with such corrosionprotected anchoring rods.

German Pat. No. 1,104,905 discloses a method of producing anchoring rods for anchoring structural parts in the earth in which a hole is made in the earth by means of a drive pipe, a tension member or anchor rod is introduced after the drive pipe has reached the final position of the bore, and thereupon the drive pipe is withdrawn while construction materials which harden in place are simultaneously introduced under pressure into the bore. With this known method, use is made of anchoring rods in which either the tension member consisting of a tension bar is connected, for instance, by threading to a drive point which is detachably seated on the drive pipe, or use is made of anchoring rods which are provided with a small sized or slender friction body in the section of the anchor rod where the tensile forces are introduced.

In order to obtain permanent anchorings of structural parts in the earth it has been found necessary to protect the tension bar from corrosion. It has therefore become known to provide the force transmission section of such an anchoring rod with a corrosion-preventing covering which in addition also serves the purpose, as a result of its smooth surface, of reducing to a minimum the friction between the tension bar and the surrounding earth in the force transmission section, which is also referred to as the free length of the anchoring rod. In this connection it has also become known to protect the force transmission section of the anchor rod by means of a smooth tube of plastic.

However, such anchoring rods have exhibited the disadvantage that the force introduction section of the anchor rod is not protected against corrosion since the sealing off of the plastic tube at the end of the force transmission section is difficult to achieve and at times moisture even passed through said seal to below the plastic tube so that corrosion became possible also in the region of the force transmission section of the anchor rod. The lack of corrosion protection in the force introduction section has proven particularly disadvantageous in the case of such anchoring rods when the force introduction section of the tension member was provided with a small sized or narrow friction body since in such case, despite the attempt to effect a proper sealing, not only the outer surface of the narrow friction body but also its inner surface and the outer surface of the tension member on which the narrow friction body is disposed were subjected to corrosion.

The object of the present invention is to provide a corrosion-protected anchoring rod in which not only is l terials is not reduced by the corrosion protection.

This purpose is achieved by an anchoring rod in which the slender friction body is developed as a corrugated tube consisting of plastic.

It has proven advisable to close the corrugated tube by provision of a bottom on the side thereof facing the earth and to connect the air end with the smooth cover ing of the force transmission section. As corrosionprotective covering for the force transmission section there is preferably used a smooth plastic tube which at its earth end is connected, for instance by welding, with the air end of the corrugated plastic tube.

The corrugated plastic tube is preferably connected with the tension member by a bonding composition which is injected into the space between the corrugated tube and the tension member. For the bonding composition, known synthetic resins or grout can be used, or else mixtures of synthetic resins with grout may be employed.

Since it has proven advantageous in the case of such anchoring rods provided with a slender friction body to develop the attachment of the narrow friction body to the tension member in such manner that the tensile forces acting on the tension member are converted over the slender friction body into compression forces which act in the surrounding earth, it is advantageous to use as the bonding composition in the region of the earth end (in the space between the tension member and the corrugated tube) a composition of greater strength than that used in the region of the air end.

Another object of the invention is to provide a method of producing anchorings in the earth in which the aforementioned anchoring rods are used in diversified fashion. I

This purpose is achieved, inter alia, by a method in which the corrugated tube is first connected with the tension member in the manner that a smooth tube of plastic is placed over the force transmission section of the tension member and connected by welding to the corrugated tube, and the anchor thus produced is installed before complete hardening of the bonding composition in known manner through a drive pipe seated in a bore hole, and the drive pipe is then withdrawn with simultaneous introduction under pressure of building materials which solidify. This method has proven particularly advantageous in cases in which the anchoring rods or parts thereof must be transported a long distance to the place of use, since, upon the transportation of anchoring rods which have been completely prefabricated for installation, there is not only the danger that the plastic tubes surrounding the tension member will be damaged, but also the danger that due to vibrations during transportation, cracks may occur in the bonding composition to weaken the connection between the corrugated tube and the force introduction section of the tension member. This formation of cracks is prevented if the bonded connection between the corrugated tube and the tension member is produced immediately before the installation of the anchoring rod, and if the installation is effected before the bonding composition has completely hardened.

It has proven advantageous, with reference to the high pressures which act on the corrugated plastic tube after the tightening of the anchoring rod, for the bonding composition between the tension member and the corrugated tube and the building materials forced under pressure into the earth around the outer region of the corrugated tube, which support the structure of the corrugated tube on both sides, to have the same strength. For this reason it is advantageous to use the same material as both the bonding composition between the tension member and the corrugated tube, and the hardenable building materials which are' injected around the force introduction section of the anchoring rod; said material may be, for instance, grout.

In view of the requirement of obtaining the same or approximately the same strength in the direct vicinity of the corrugated tube on the inside and outside thereof by the use of the same material as bonding composition and as grouting material, it is advantageous to create equal pressure conditions upon the grouting of the space between the tension member and the corrugated tube, and the introduction of the hardenable building materials in the outer region on the earth end of the corrugated tube. This result is obtained by employing a bundle of steel bars surrounding an injection tube as the tension member.

Prior to insertion into the bore hole, this tension member is preferably pushed into the interconnected tubes of plastic, without the corrugated tube being connected with the tension member in the region of the force introduction section. These parts of the anchoring rod composed in this manner are thereupon introduced by the drive pipe into the bore hole, and the space between the tension member and the corrugated tube (by use of the injection tube) and the outer region on the earth end of the corrugated tube (by the use of the drive pipe) are simultaneously grouted with building materials which harden in place.

When using single steel-bar members as tension members there has proven satisfactory a method in which the corrugated tube of the force introduction section and the smooth tube of plastic serving as covering for the force transmission section are connected, for instance by welding, with each other prior to insertion into the bore hole, whereupon the interconnected parts, after the end position of the bore hole has been reached, are forced into the drive pipe. The bonding composition is then introduced into the corrugated tube by means of an injection tube introduced into the plastic tube, and thereupon the tension member is introduced into the final position in the interconnected parts. Thereupon the drive pipe is removed in known manner with simultaneous introduction under pressure through the drive pipe of building materials which harden in place.

By the use of a corrugated tube of plastic as the small sized or slender friction body there is not only obtained a permanent effective corrosion protection of the tension member in the region of the force introduction section, but at the same time, the slender friction body required is formed by the plastic tube which in itself serves only for corrosion protection. It has namely, surprisingly, been found, as a matter of fact that a corrugated plastic tube is suitable as a friction body for the introduction into the surrounding earth of considerable I tensile forces which, depending on the development of the anchoring rod, are within the order of magnitude of between 30 and tons, even though such a tube would, on basis of the material of which it is made, appear entirely incapable of transmitting such high tensile forces. For this reason, in accordance with the methods and anchoring rods known up to now, there have been used as the friction body only corrugated tubes of steel, or the tension bar itself has been developed as slender friction body in the force introduction region by the rolling thereon of ribs or the cutting of threads therein. Accordingly, there were considerable reservations with respect to the use of a corrugated plastic tube as a friction body. However, these reservations were overcome by the development of the anchoring rod in accordance with the subject invention and the method of the invention, in which the essential thing is that the corrugated plastic tube is supported on one side by the bonding composition and on the other side thereof with the injected hardening building materials in the outer region.

For further explanation of the invention reference is had to an embodiment shown by way of example in the accompanying drawings in which:

FIG. 1 is a cross section through an anchoring rod installed in the earth;

FIG. 2 is a view on a larger scale of the earth end of the force introduction section of the anchoring rod, seen in longitudinal section;

FIG. 3 is a cross section through the anchoring rod in the region of the force introduction section in which a bundle of steel rods has been used as tension member; and

FIG. 4 is a schematic showing in longitudinal section of the grouting head seated on the air end of the drive pipe and having a tension member consisting of a bundle of steel rods and located in the drive pipe.

Referring to FIG. 1, the anchoring rod 1 consists of a tension member 2, the earth-side end of which is externally surrounded in the region of the force introduction section 3 by building materials 4 which have been injected into the earth and harden in place. The anchoring rod 1 is braced at its air end by means of an anchor head structure 6 against a timbering 5 supporting an excavation, for instance, an embankment.

The tension member 2 is covered over its free end, i.e., the force transmission section 7, by a smooth plastic tube 8 serving as a corrosion-protection member. On the tension member 2 there is seated, on the force introduction section 3, a corrugated plastic tube 9 which is connected at the joint 10 with the smooth plastic tube 8, for instance by welding. The corrugated plastic tube 9 defines the small sized or narrow friction body of the anchoring rod.

As can be noted from FIG. 2, the corrugated plastic tube 9 is closed at its earth end by a bottom 11. The space between the corrugated plastic tube 9 and the tension member 2 is filled with a bonding composition 12.

In FIG. 3 there is shown the tension member 2 which consists of a bundle of steel bars 13 having at its center an injection tube 14.

FIG. 4 shows the air end of the anchoring rod 1, which in this case consists of a bundle of steel bars 13 arranged around an injection tube 14 during the injection of hardenable building materials into the space between the tension member 2 and the corrugated plastic tube 9, and the simultaneous introduction of hardenable building materials 4 into the region of the force introduction section 3 of rod 1. The anchoring rod 1 is seated in the drive pipe onto which there is screwed an injection head 16 which is connected by a hose 17 with an injection pump (not shown).

While the invention has been shown and illustrated in its several preferred embodiments, and has included certain details, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as claimed:

What is claimed is:

1. A method of making an earth-anchoring, including the steps of:

providing a corrosion-protected earth anchoring including an elongated tension member having a force introduction section adjacent one end thereof, and a force transmission section adjacent the opposite end thereof;

placing a smooth plastic tube over the force transmission section of the tension member;

placing a corrugated tube, closed at one end, over the force introduction section of said tension member, and connecting same to said smooth plastic tube to form a continuous covering over the tension member;

injecting hardenable building materials in the space between the corrugated tube and the force introduction section of the tension member;

driving a drive pipe into the earth to form a bore hole;

installing, prior to the hardening of said building materials, said tension member in the drive pipe; and withdrawing the drive pipe from the bore hole while simultaneously injecting hardenable building materials in the bore hole in the vicinity of the force introduction section of the tension member externally of the corrugated tube. 2. A method of making an earth anchoring as in claim 1 wherein the same hardenable building materials are injected between the tension member and the corrugated tube, and externally of the corrugated tube in the vicinity of the force introduction section of the tension member.

3. A method of making an earth anchoring as in claim 1 wherein the tension member comprises an array of steel bars surrounding an injection tube, and wherein the building materials are simultaneously injected externally of the corrugated tube in the vicinity of the force introduction section of the tension member, and by said injection tube into the space between the corrugated tube and said array of steel bars.

4. A method of making an earth anchoring including the steps of:

providing a corrosion-protection member by fusing a smooth tube of plastic to a corrugated tube of plastic of which the other end is closed;

driving a drive pipe into the earth to form a bore hole;

inserting said corrosion protection member, beginning with its corrugated portion, into said bore hole inside said drive pipe;

introducing hardenable building materials into said corrosion-protection member and inserting a metallic tension member therein extending from the immediate neighborhood of the closed end of said corrugated tube to the immediate neighborhood of the open end of said smooth tube; and

withdrawing said drive pipe from said bore hole while simultaneously injecting hardenable building materials in the bore hole externally of said corrugated tube. 

1. A method of making an earth-anchoring, inclUding the steps of: providing a corrosion-protected earth anchoring including an elongated tension member having a force introduction section adjacent one end thereof, and a force transmission section adjacent the opposite end thereof; placing a smooth plastic tube over the force transmission section of the tension member; placing a corrugated tube, closed at one end, over the force introduction section of said tension member, and connecting same to said smooth plastic tube to form a continuous covering over the tension member; injecting hardenable building materials in the space between the corrugated tube and the force introduction section of the tension member; driving a drive pipe into the earth to form a bore hole; installing, prior to the hardening of said building materials, said tension member in the drive pipe; and withdrawing the drive pipe from the bore hole while simultaneously injecting hardenable building materials in the bore hole in the vicinity of the force introduction section of the tension member externally of the corrugated tube.
 2. A method of making an earth anchoring as in claim 1 wherein the same hardenable building materials are injected between the tension member and the corrugated tube, and externally of the corrugated tube in the vicinity of the force introduction section of the tension member.
 3. A method of making an earth anchoring as in claim 1 wherein the tension member comprises an array of steel bars surrounding an injection tube, and wherein the building materials are simultaneously injected externally of the corrugated tube in the vicinity of the force introduction section of the tension member, and by said injection tube into the space between the corrugated tube and said array of steel bars.
 4. A method of making an earth anchoring including the steps of: providing a corrosion-protection member by fusing a smooth tube of plastic to a corrugated tube of plastic of which the other end is closed; driving a drive pipe into the earth to form a bore hole; inserting said corrosion protection member, beginning with its corrugated portion, into said bore hole inside said drive pipe; introducing hardenable building materials into said corrosion-protection member and inserting a metallic tension member therein extending from the immediate neighborhood of the closed end of said corrugated tube to the immediate neighborhood of the open end of said smooth tube; and withdrawing said drive pipe from said bore hole while simultaneously injecting hardenable building materials in the bore hole externally of said corrugated tube. 